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M31ROSXRAY: Help

M31ROSXRAY - ROSAT PSPC M31 Source Catalog


Overview

This catalog is the complete ROSAT PSPC Source List of X-ray sources found in two surveys of M 31 reported by Supper et al. (1997, 2001). These papers reported the results of the analysis of the two ROSAT PSPC surveys of M 31 performed in the summers of 1991 and 1992, respectively. summer 1992. Supper et al. (2001) compare and combine the results from the two surveys. In the first survey, 396 X-ray point sources were detected, and an identical number in the second survey, although this equality is coincidental, as the source lists are different and contain only 239 sources in common.

Within the approximately 10.7 square degrees field of view of the second survey, 396 individual X-ray sources were detected, of which 164 sources were new detections. When combined with the first survey, this resulted in a total of 560 X-ray sources in the field of M 31. Their (0.1 keV-2.0 keV) fluxes range from 7 x 10^(-15) to 7.6 x 10^(-12) erg cm^(-2) s^(-1), and of these 560 sources, 55 are tentatively identified with foreground stars, 33 with globular clusters, 16 with supernova remnants, and 10 with radio sources and galaxies (including M 32). A comparison with the results of the Einstein M 31 survey reveals 491 newly detected sources, 11 long-term variable sources, and 7 possible transient sources. Comparing the two ROSAT surveys, Supper et al. come up with 34 long-term variable sources and 8 transient candidates. For the M 31 sources, the observed X-ray luminosities range from 4 x 10^(35) to 4 x 10^(38) erg s^(-1). The total (0.1 keV-2.0 keV) luminosity of M 31 is (3.4 +/- 0.3) x 10^(39) erg s^(-1), distributed approximately equally between the bulge and disk. Within the bulge region, the luminosity of a possible diffuse component combined with faint sources below the detection threshold is (2.0 +/- 0.5) x 10^(38) erg s^(-1). An explanation in terms of hot gaseous emission leads to a maximum total gas mass of (1.0 +/- 0.3) x 10^6 solar masses.

The conversion of PSPC count rates into X-ray fluxes depends on the assumed spectral shape. For M 31-sources, a power law with photon index of -2.0 and an intervening column density pf 9 x 10^(20) H atoms cm^(-2) may be used, leading to the conversion factor of 1 ct/ksec = 3.00 x 10^(-14) erg cm^(-2) s^(-1) in the 0.1-2.0 keV broad band. For foreground stars, the application of this conversion factor leads to an over-estimate of the fluxes.


Catalog Bibcode

2001A&A...373...63S

References

ROSAT PSPC survey of M31.
    Supper R., Hasinger G., Pietsch W., Truemper J., Jain, A., Magnier E.A.,
    Lewin W.H.G., and van Paradijs J.,
   <Astron. Astrophys. 317, 328 (1997)>
   =1997A&A...317..328S
The second ROSAT PSPC survey of M31 and the complete ROSAT PSPC source list.
    Supper R., Hasinger G., Lewin W.H.G., Magnier E.A., van Paradijs J.,
    Pietsch W., Read A.M., Truemper J.
   <Astron. Astrophys. 373, 63 (2001)>
   =2001A&A...373...63S

Provenance

This online catalog was created by the HEASARC in October 2001 based on machine-readable tables obtained from the ADC/CDS data centers (their catalog J/A+A/373/63, and table table6.dat).

Parameters

Source_Flag
Source classification flag with the following meanings:

         a: Foreground star
         b: Galaxy
         c: Supersoft source candidate
         d: Globular cluster
         e: SNR
         f: Bulge source
         v: Variable source (ref. Table2, 3 and footnote in Sect. 4.1.1)
         u: Source with uncertain count rate
  
Notice that the HEASARC has changed the last three symbols (f, v, and u) from their non-alphabetic values (*, ~, and +, respectively) in the original catalog.

Name
The M 31 X-ray source name derived from the standard prefix for ROSAT X-ray sources of 'RX' and a numeric string based on the J2000 positional coordinates.

Einstein_Flag
A flag that is set to 'Y' to indicate that the source was correlated with an Einstein X-ray source. Notice that the HEASARC has changed this value from the non-alphabetic value of '*' in the original catalog.

S2_Number
The source number in the Second Survey (S II) of M31 as given in Table 5 of Supper et al. (2001).

S1_Number
The source number in the First Survey (S I) of M31 as given in Table 5 of Supper et al. (1997).

Survey_Flag
This is a data identification marker flag with possible values of '+', '-', or ' ' corresponding to the following rubric:

      '+' = Source was seen in both surveys and listed data are
            from the first survey.
      '-' = Source was seen in both surveys and listed data are
            from the second survey.
    blank = Source was *only* seen in one of the surveys (the one with the
            non-null survey number), and the listed data are from it
  

RA
The Right Ascension of the X-ray source in the selected equinox. This was given in J2000 coordinates to a precision of 0.1 seconds of time in the original catalog.

Dec
The Declination of the X-ray source in the selected equinox. This was given in J2000 coordinates to a precision of 1 arcsecond in the original catalog.

LII
The Galactic Longitude of the X-ray source.

BII
The Galactic Latitude of the X-ray source.

Error_Radius
The 1-sigma uncertainty in the source position, in arcseconds. The calculation of this positional uncertainty is based on the maximum likelihood algorithm and incorporates the effects of statistical errors depending on the number of source counts, together with the blur radius of the point spread function (PSF) at the off-axis angle and the mean photon energy of the source. A minimum threshold of 5 arcseconds is also set to account for a systematic positional error.

Quality_Flag
A classification of the quality of the detection.This is differently defined for sources in the two surveys, notice.

For sources found in the first survey, the classification parameter is as follows: class 1 identifies sources detected in the central region of the PSPC with off-axis angles <= 20 arcminutes, class 2 defines locations of sources found between 20 and 40 arcminutes, and class 3 contains sources with off-axis angles > 40 arcminutes. As mentioned in Sect. 2 of Supper et al. (1997), the source position was derived from the pointing in which it appears at the lowest off-axis angle, i.e., with the best class (though not under a PSPC rib). For sources in class 2 and especially class 3, any upper limit in the listed count rates can even be an underestimation due to the wider PSF and the therefore higher possibility of rib influencies.

For sources found in the second survey, the listed classification parameter is defined class 1 for sources detected in the inner PSPC region (20 arcminutes radius) and class 4 for sources outside this region.

The caveats for the first survey source catalogue mentioned in Supper et al. (1997) are still valid whenever these sources are not replaced by second survey detections.

Max_Likelihood
The highest likelihood of existence found in any of the five energy bands as computed with the maximum likelihood method.

Rate_B_Flag
A flag that is set to '<' to indicate an upper limit on the broad-band count rate.

Rate_B
The broad-band (0.1-2.0 keV) count rate in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Because some faint sources were not detected in all energy bands (i.e., these sources had a likelihood below the threshold value of 10 in one or more energy bands), in such cases 1-sigma upper limits to the count rates are presented. These upper limits are computed from the 1-sigma fluctuations (Poissonian statistics) of the background counts at the source position and are indicated by the corresponding rate flag parameter (rate_b_flag in this case) having a value of <.

Rate_B_Error
The statistical 1-sigma Error in the broad-band count rate, in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Notice that the listed count rate errors are only the statistical errors, whereas the systematical errors are expected to be less than +/- 15%.

Rate_S_Flag
A flag that is set to '<' to indicate an upper limit on the soft-band count rate.

Rate_S
The soft-band (0.1-0.4 keV) count rate in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Because some faint sources were not detected in all energy bands (i.e., these sources had a likelihood below the threshold value of 10 in one or more energy bands), in such cases 1-sigma upper limits to the count rates are presented. These upper limits are computed from the 1-sigma fluctuations (Poissonian statistics) of the background counts at the source position and are indicated by the corresponding rate flag parameter (rate_s_flag in this case) having a value of <.

Rate_S_Error
The statistical 1-sigma Error in the soft-band count rate, in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Notice that the listed count rate errors are only the statistical errors, whereas the systematical errors are expected to be less than +/- 15%.

Rate_H_Flag
A flag that is set to '<' to indicate an upper limit on the hard-band count rate.

Rate_H
The hard-band (0.5-2.0 keV) count rate in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Because some faint sources were not detected in all energy bands (i.e., these sources had a likelihood below the threshold value of 10 in one or more energy bands), in such cases 1-sigma upper limits to the count rates are presented. These upper limits are computed from the 1-sigma fluctuations (Poissonian statistics) of the background counts at the source position and are indicated by the corresponding rate flag parameter (rate_h_flag in this case) having a value of <.

Rate_H_Error
The statistical 1-sigma Error in the hard-band count rate, in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Notice that the listed count rate errors are only the statistical errors, whereas the systematical errors are expected to be less than +/- 15%.

Rate_H1_Flag
A flag that is set to '<' to indicate an upper limit on the 0.5-0.9 keV band count rate.

Rate_H1
The Hard1-band (0.5-0.9 keV) count rate in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Because some faint sources were not detected in all energy bands (i.e., these sources had a likelihood below the threshold value of 10 in one or more energy bands), in such cases 1-sigma upper limits to the count rates are presented. These upper limits are computed from the 1-sigma fluctuations (Poissonian statistics) of the background counts at the source position and are indicated by the corresponding rate flag parameter (rate_h1_flag in this case) having a value of <.

Rate_H1_Error
The statistical 1-sigma Error in the 0.5-0.9 keV band count rate, in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Notice that the listed count rate errors are only the statistical errors, whereas the systematic errors are expected to be less than +/- 15%.

Rate_H2_Flag
A flag that is set to '<' to indicate an upper limit on the 0.9-2.0 keV count rate.

Rate_H2
The hard2-band (0.9-2.0 keV) count rate in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Because some faint sources were not detected in all energy bands (i.e., these sources had a likelihood below the threshold value of 10 in one or more energy bands), in such cases 1-sigma upper limits to the count rates are presented. These upper limits are computed from the 1-sigma fluctuations (Poissonian statistics) of the background counts at the source position and are indicated by the corresponding rate flag parameter (rate_h2_flag in this case) having a value of <.

Rate_H2_Error
The statistical 1-sigma Error in the 0.9-2.0 keV band count rate, in counts per second (ct/s). This was converted by the HEASARC from the counts per kilosecond unit given in the original catalog. Notice that the listed count rate errors are only the statistical errors, whereas the systematic errors are expected to be less than +/- 15%.

Class
The HEASARC Browse Object Classification, derived in this case from the value of the source_flag parameter. Only a small fraction of the sources in this catalog have classification information.


Contact Person

Questions regarding the M31ROSXRAY database table can be addressed to the HEASARC User Hotline.
If you have any problems, please consult the help page or mail ledas-help@star.le.ac.uk
 
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